The objective of this project is to characterize not only the extent to which reduced physiologic capacity (e.g., cardiopulmonary function, muscle strength) and physical performance capacity (e.g., tests of balance, walking speed) relate to physical functioning in the elderly, but also the extent to which social factors and health status are important mediators in the relationship between physical capacity (the aggregate of physiologic and performance capacities) and physical functioning. This competing continuation application presents plans to extend a community-based, longitudinal study of non-institutionalized persons aged >55 years. The main focus is on the importance of physical activity in the maintenance of physical functioning in the elderly and its importance with regard to morbidity and mortality sparing effects. An additional focus is on factors that relate to physical function maintenance and recovery after deteriorations in health status or social conditions. These points of focus are captured in a conceptual model that serves to guide the Specific Aims and the analyses of the study data. A community-based sample of 2092 subjects, >55 years (med. 70 yr), has been recruited and 2 evaluations have been completed. The 91.2% of the subjects, who remain in the study will be followed for 2 further evaluations (F3, F4) spanning 3 years. Evaluation will include an in-home assessment (demographics, social factors, medical history, medications, smoking, alcohol, 7 day & 12 month physical activity profile, self-reported function, direct physical and cognitive performance measures, anthropometrics, peak flow, and blood pressure) and a laboratory evaluation (isokinetic muscle strength of muscles for gait, visual testing, forced expiratory maneuvers, and treadmill exercise). Statistical analyses of the data will be based on two approaches. Mixed linear models will be used to evaluate changes in quantitative outcomes (e.g., physical function scores, energy expenditure in physical activity) in terms of baseline and time-dependent changes in physical capacity, social factors and health status. Gender-specific effects also will be evaluated. Transition models will be used to evaluate the dynamic transitions of physical functional status over the period of the four evaluations.